PWM driving 12V DC motors with 24V power supply

Thread Starter

us202000

Joined Jul 5, 2011
16
Hi, all,

I have a question whether I can use PWM to drive 12V DC motors with 24V battery power supply as in the case of robot with H-bridge. An example would be a car windshield wiper or power window motor types which are normally operated at 12v. I searched for similar discussions and found one interesting statement by Pedant Engineer: "So if you wanted to run a 12V motor from 24V just keep the PWM duty cycle below 50% and you are good to go. Be careful though not to push this too hard." from https://forum.allaboutcircuits.com/threads/are-switching-power-supplies-good-for-powering-motors.167365/

This sounds like the answer to my question but I want to check to see whether anyone has tried this in practice. There are real good reasons why a 24V DC power is more desirable. For one thing, it works better for the MOSFETs so the gate voltage doesn't easily drop below 10v. I have both 24v and 12v motors so it would be nice to keep just one power source at the same voltage.

Any comments would be greatly appreciated.

Thanks.
 

MaxHeadRoom

Joined Jul 18, 2013
20,936
You should always go higher with supply voltage for PWM driven DC motors, the motors will tolerate higher voltage as long as the RPM is not exceeded too much, and any resultant current does not exceed the continous RPM rating.
Max.
 

Reloadron

Joined Jan 15, 2015
5,513
"So if you wanted to run a 12V motor from 24V just keep the PWM duty cycle below 50% and you are good to go. Be careful though not to push this too hard."
That would be correct and depending on motor, as Max mentions you can exceed 50% by a slight margin. Motors, especially heavy motors are pretty forgiving creatures. As stated, just don't push too hard.

Ron
 

MaxHeadRoom

Joined Jul 18, 2013
20,936
Yes, Generally a 12v motor is not going to be harmed by 24v, IF it is not allowed to go above its rated RPM by monitoring the motor, both rpm and current and keeping it withing the manuf. specs..
Max.
 
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